Earthquakes 101…and is the big one coming?
WEST MICHIGAN — We’ve been hearing plenty about earthquakes over the last few months around the world, but rarely do we have much earthquake news to talk about here in Michigan. Yes…we have felt the ground shake from time to time here in Michigan…so not unusual, but rare to have it actually occur within the state. The last time we had a sizable quake occur in the state was August 9, 1947. We measured a 4.6 on the Richter Scale at that time across southern lower Michigan.
To understand what’s happening, we need to explain the basics. We know lithopspheric plates are moving each and everyday across the surface of the earth. These plates can converge with one another, diverge, or slip past each other (transform fault). Where an oceanic and continental plate converges, one plate is being subducted or pulled underneath another plate and literally being destroyed. If two continental plates converge, mountains can form and earthquakes can result. Our West Michigan quake was not the result of either of these.
In fact, there may be several very small, inactive faults, or cracks in the rock below the surface in Michigan, but there are simply no forces acting on them to create routine earthquakes. There are two known seismic zones in the Midwest. One in Indiana known as the Wabash Valley Seismic Zone, and the more well-known one called the New Madrid (pronounced Mad-Dread) in Missouri. There’s been plenty of activity in these locations over hundreds of years…in fact about 200 quakes each year occur in these areas. Michigan has felt quakes that originated in these areas, but without a direct active fault here it is rare to see one originate here. We may never know what created the 4.2 magnitude quake around Galesburg on Saturday, but we know a major quake in this state is highly unlikely.
According to Western Michigan University Geosciences Professor Dave Barnes “Michigan sits just about in the bulls-eye of about the lowest potential for significant damage to anywhere in the United States. So we have very little to worry about.”
Many have been asking about hydraulic fracking playing a role in this latest Michigan quake, but that too is highly unlikely. Why? Barnes says “there is simply no drill rig in the state that’s ever drilled six miles below the surface. There is no relationship between hydraulic fracturing and this earthquake event.” The depth of this earthquake is between four and six miles.
Where’s the highest hazard or bulls-eye for earthquakes in this part of the United States? (see thumbnail attached to this story) Exactly where the two seismic zones are located to our south/west. While the big one is possible in these areas, Michigan would likely only feel the secondary shake from a larger quake well outside of the state. To restate the obvious, the events that take place with earthquakes around the world in places like Japan, Indonesia, Nepal, Haiti, and California are fundamentally completely different geologically than what can happen in Michigan. We simply lack the tectonic activity and plate boundaries that are present in other parts of the world!